As means for slicing off wafers from a workpiece such as a silicon ingot or a compound semiconductor ingot, wire saws have been conventionally known. In each of the wire saws, a wire row is formed by winding a slicing wire around a plurality of rollers in many turns, the slicing wire is driven in an axial direction at a high speed, and a workpiece is fed to the wire row for slicing while appropriately supplying slurry, whereby this workpiece is sliced at respective wire positions at the same time (see, e.g., Patent Literature 1).
Here, FIG. 3 shows an outline of an example of a conventional general wire saw. As shown in FIG. 3, this wire saw 101 is mainly constituted of a wire 102 (a high tensile steel wire) to slice a workpiece W, a wire row 104 formed by winding the wire 102 around a plurality of grooved rollers 103 and 103′, tension imparting mechanisms 105 and 105′ to impart tension to the wire 102, a workpiece feed mechanism 106 which feeds the workpiece W to be sliced toward a lower side, and a slurry supply mechanism 107 which supplies slurry having GC (silicon carbide) abrasive grains or the like dispersed in a liquid at the time of slicing.
The wire 102 is reeled out from one wire reel 108, and reaches the grooved roller 103 through the tension imparting mechanism 105. The wire 102 is wound around this grooved roller 103 in approximately 300 to 400 turns, and then taken up by the wire reel 108′ through the other tension imparting mechanism 105′.
Further, the grooved roller 103 is a roller provided by press-fitting a polyurethane resin around a cylinder made of iron and steel and forming grooves on a surface thereof at a fixed pitch. The grooved roller 103 is configured in such a manner that the wound wire 102 can be driven in a reciprocating direction in a predetermined cycle by a driving motor 111.
It is to be noted that, at the time of slicing the workpiece W, the workpiece W is held and pushed down by the workpiece feed mechanism 106, and fed to the wire row 104 wound around the grooved rollers 103 and 103′. Such a wire saw 101 is used, appropriate tension is applied to the wire 102 by the tension imparting mechanism 105, the slurry fed from the slurry supply mechanism 107 is supplied through nozzles 109 while allowing the wire 102 to travel in the reciprocating direction by the driving motor 111, and the workpiece is fed for slicing by the workpiece feed mechanism 106, thereby slicing the workpiece.
On the other hand, there is also known a method for slicing a workpiece by using a fixed abrasive grain wire having diamond abrasive grains or the like secured to a surface of the wire in place of using slurry containing abrasive grains, and this has been partially put into practical use for slicing of small-diameter ingots each having a diameter of approximately 150 mm or less.
In this slicing using the fixed abrasive grain wire, a general wire saw can be used as it is by attaching the fixed abrasive grain wire in place of the steel wire of the wire saw shown in FIG. 3 and changing the slurry to a coolant such as cooling water which does not contain abrasive grains.